Scientific schematic of an ultrasonic array showing transmission and reception with red and blue elements.

Scientific schematic illustration of a Row–Column Addressed (RCA) ultrasonic array for orthogonal plane wave imaging. The RCA probe consists of two orthogonal and coexisting sets of elongated rectangular elements: column elements (red) and row elements (blue), forming a fixed cross-grid array. Both row and column elements are always physically present throughout the entire acquisition process. On the left side, the illustration shows the column elements acting as transmitters, generating tilted plane waves with clearly visible oblique planar wavefronts propagating into the medium, while the row elements simultaneously act as receivers, capturing the backscattered acoustic waves. Importantly, the non-transmitting elements remain visible and inactive rather than disappearing, emphasizing the inherent structure of the RCA array. On the right side, a symmetric and complementary acquisition mode is depicted, where row elements transmit tilted plane waves and column elements receive echoes, while both element sets remain physically present in the probe geometry. The two acquisition schemes are shown side-by-side to illustrate orthogonal plane wave (OPW) transmission–reception switching, rather than two separate probes or array configurations. The imaging medium is represented as a semi-transparent solid block with faint internal scatterers, and acoustic propagation is visualized using semi-transparent wavefronts and directional arrows, indicating beam steering and coherent See more